Yoo, M.-J., X. Liu, J. C. Pires, P. S. Soltis, and D. E. Soltis. 2014. Nonadditive Gene Expression In Polyploids. Annual Review of Genetics 48: In Press [Link to article on publisher’s site]

Polyploidy, specifically allopolyploidy, involves hybridization and duplication of divergent parental genomes and provides new avenues for gene expression. The expression levels of duplicated genes in polyploids can show deviation from parental additivity (the arithmetic average of the parental expression levels). Nonadditive expression comprises two possible scenarios: (a) the total gene expression level in a polyploid is similar to that of one of its parents, indicating down-regulation of one parental genome, and (b) total gene expression in a polyploid is lower or higher than in either parent (homoeolog expression bias). The former is further classified into expression level dominance and transgressive expression. Non-additive gene expression has been widely observed in diverse polyploids. Several factors may result in expression non-additivity in polyploids, including maternal-paternal influence, gene dosage balance, cis– and/or trans-regulatory networks, and epigenetic regulation. As our understanding of non-additive gene expression in polyploids remains limited, a new generation of investigators should explore additional phenomena (i.e., alternative splicing) and use other high-throughput ′omics technologies to measure the impact of non-additive expression on phenotype, proteome, and metabolome.